1. Field of the Invention
The present invention relates to a magnetic recording medium, which is formed with a magnetic layer including resin coated on one surface of a non-magnetic substrate (base film), and particularly relates to a magnetic recording medium being able to realize excellent magnetic characteristics if it is utilized for digital recording, which demands high density recording.
2. Description of the Related Art
In a magnetic tape as a magnetic recording medium used for a video tape recorder (referred to as VTR), hereinafter a magnetic recording medium is generically referred to a magnetic tape, a thickness of magnetic tape is necessary to be as thin as possible in order to extend a recording time. However, if the thickness itself is simply thinned, a mechanical strength of magnetic tape is deteriorated. The deteriorated mechanical strength causes problems such that an electromagnetic conversion characteristic is deteriorated by a worse contacting condition of the magnetic tape with a magnetic head, and such that the magnetic tape may be damaged, folded or wrinkled by a collision of the magnetic tape with a tape guide, which regulates tape traveling.
In order to solve the problems mentioned above, several countermeasures have been tried such as reinforcing polyester film utilized for a non-magnetic substrate supporting a magnetic layer and improving a mechanical strength of magnetic tape by forming a magnetic layer having a higher modulus of elasticity. However, result of improvement with respect to the above-mentioned problems was unsatisfactory. Therefore, there provided several prior arts, for example, the Japanese Patent Application Laid-open Publications No. 56-11624/1981 and No. 62-62424/1987 disclose that aramid resin is utilized for a non-magnetic substrate, No. 63-298810/1988 discloses that the Young""s modulus in the transverse direction (hereinafter referred to TD) of a substrate is designated to be larger than the Young""s modulus in the longitudinal direction (hereinafter referred to MD), wherein the Young""s modulus in the TD and MD is referred to the TD Young""s modulus and the MD Young""s modulus respectively, and No. 4-44628/1992 discloses that the TD and MD Young""s moduli are set to approximately 7.8 GN/m2 respectively.
Further, in accordance with a shift of signal system for recording and reproducing by a VTR from analog over to digital, With respect to a magnetic tape in the future, a demand for extending a recording time of a magnetic tape in the future is increasing in a digital format as same manner as in an analog format. However, no actual suggestion for realizing the extension of recording time has been provided.
In a magnetic tape of the prior art mentioned above, such a configuration utilizing an aramid resin film as a non-magnetic substrate generates a problem such that a manufacturing cost of the aramid resin film is expensive and the aramid resin film is bard to utilize commonly because the aramid resin film is inferior in productivity.
Further, in a conventional magnetic tape, an optimum contacting condition of the magnetic tape with a magnetic head can not be maintained, so that an electromagnetic conversion characteristic between the magnetic tape and the magnetic head is deteriorated in accordance with that a total thickness of the magnetic tape becomes thinner even though the TD Young""s modulus of a non-magnetic substrate is constituted to be more than the MD Young""s modulus. Thus, there existed another problem such that a longer recording time of a VTR is hard to be realized by thinning a thickness of the magnetic tape. The total thickness of a magnetic tape mentioned above is a thickness of the magnetic tape in total, for example, the total thickness is a thickness of a back coating layer, a non-magnetic substrate (base film) and a magnetic layer laminated in sequence.
Furthermore, in a conventional magnetic tape, both of the above-mentioned electromagnetic conversion characteristic and a mechanical strength of magnetic tape are deteriorated if the total thickness becomes less than 14 xcexcm even though the TD and MD Young""s moduli are constituted to be approximately 7.8 GN/m2. Consequently, there existed a further problem such that a longer recording time of a VTR is hard to be realized by thinning a thickness of the magnetic tape.
Moreover, in a magnetic tape utilized for recording a digital signal, a physical condition to be observed while recording or reproducing such as a space loss, which is a distance between a magnetic recording medium (magnetic tape) and a magnetic head, is required more strictly. Therefore, there existed a furthermore problem such that a conventional magnetic recording medium can hardly improve a reproduction output or characteristics of error and a microscopic dropout (D/O) of xe2x88x926 dB and 0.5 xcexcs. The D/O is a phenomenon that a level of reproduction output of magnetic tape decreases intermittently, wherein the reproduction output is essentially outputted continuously. The xe2x80x9cxe2x88x926 dB and 0.5 xcexcsxe2x80x9d represents that a state of signal is counted as a dropout (D/O), wherein a signal output decreases by more than 6 dB with respect to an original signal level and such a signal output condition continues for a period of more than 0.5 xcexcs.
In a VTR of the VHS system as a conventional video tape recorder of the analog format, a conspicuous D/O on a screen is regulated as xe2x88x9216 to xe2x88x9220 dB and 5 to 15 xcexcs. However, in a case that a signal to be recorded is changed from analog over to digital, an error rate of digital reproduction signal is influenced by a microscopic D/O of signal. Thus, a minute D/O such as xe2x88x926 dB and 0.5 xcexcs should be reduced. A D/O of xe2x88x926 dB and 0.5 xcexcs is small in signal reduction to be regulated in comparison with a criterion of measurement of conventional D/O such as xe2x88x9216 to xe2x88x9220 dB and 5 to 15 xcexcs, so that the smaller dropout is called a microscopic D/O.
Accordingly, in consideration of the above-mentioned problems of the prior arts, an object of the present invention is to provide a magnetic recording medium, which is excellent in an electromagnetic conversion characteristic and exhibits excellent characteristics such that an error rate is decreased even when recording or reproducing a digital signal and a microscopic D/O (dropout) is decreased by reducing occurrence of possible damage to the magnetic recording medium while running and keeping mechanical contact of the magnetic recording medium with a magnetic head in an excellent condition even though a total thickness of the magnetic recording medium is thinner than the standard in order to realize a longer period of recording time of a signal.
In order to achieve the above object, the present invention provides, according to an aspect thereof, a magnetic recording medium comprising: a tape shaped non-magnetic substrate; and a magnetic layer formed by coating magnetic powder and resin mixed and dispersed on one surface of the non-magnetic substrate, the magnetic recording medium is further characterized in that a total thickness of the magnetic recording medium is within a range of more than 9.0 xcexcm and less than 12.3 xcexcm, and that a thickness of the magnetic layer is within a range of more than 1.3 xcexcm and less than 2.0 xcexcm, and that a Young""s modulus in the traverse direction (TD) of the non-magnetic substrate is within a range of more than 15.6 GN/m2 and less than 19.6 GN/m2.
Other object and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanied drawings.